Temporary pacing is performed in patients having cardiac arrhythmias as a bridge to permanent pacing or to recovery; temporary pacing also provides prophylactic utility for specific medical procedures including, for example, transcatheter aortic valve replacement (TAVR) procedures. Such arrhythmias can manifest as bradycardia or tachycardia and can result in hemodynamic instability to the patient. Often bradycardia can occur as a result of sinus node dysfunction or atrioventricular block. Acute therapy can be obtained via placement of a temporary lead in the right ventricle (RV); the temporary pacing lead receives an electrically generated signal from an external pulse generator located external to the patient.
Current temporary pacing leads are generally placed via a percutaneous transvenous access, via a direct epicardial placement of the electrode via a surgical access site or transcutaneous using patches placed on the body surface, i.e., skin. The pacemaker lead can be a unipolar lead with the negative or cathode electrode located at or near its distal end; alternately, the lead can be a bipolar lead thereby containing both the negative cathode and the positive anode on the lead body separated by a small distance of a few millimeters. The unipolar lead requires that a separate anode be located adjacent the subcutaneous tissue at a remote location located several inches away from the cathode. The unipolar lead provides for a greater ease of capture of the electrical pulse by the myocardium from the pacemaker generator and hence is often used for temporary pacing. The bipolar lead provides a benefit over the unipolar lead for requiring a lower threshold energy to obtain capture and hence has greater application for permanent pacing with a preserved battery life for the implanted pulse generator.
Temporary pacing leads can have active fixation elements such as a distally located screw-shaped electrode that is screwed into the myocardium. Such active fixation can hold the lead in place but is also more difficult to place during implantation and more difficult to remove after a few days. Active fixation leads carry a greater likelihood of myocardial perforation and potential for tamponade. Temporary leads can also have passive fixation such as tines that are designed to be entangled within the trabeculae of the endocardial surface to provide adequate lodging and also can be time-consuming to place. Other temporary leads are more easily and quickly placed without active or passive fixation elements but still require fluoroscopy and are easily dislodged by small movements of the pacing lead in relation to the patient thereby resulting in loss of capture of the electrical stimulus from the pacemaker generator even due to small micro-dislodgements. Temporary pacing leads can also have flow-directed balloons located near the distal end to assist with advancement of the pacing lead in the RV chamber but difficult to adequately position for capture and thus require a significant amount of manipulation under fluoroscopy for optimal positioning; flow-directed balloons are less reliable for providing a preferred location for the pacing lead.
Current temporary pacing leads often have a general linear configuration near the distal region of the lead. A slight curve can be formed into the lead to allow it to lay against the wall of a heart chamber such as the right ventricle (RV). Due to the linear configuration, the distal end of the temporary lead can be traumatic to the heart wall and can protrude, penetrate, or perforate through the wall of the heart leading to potential tamponade and which can lead to death of the patient. Placement of such linearly configured leads is performed under fluoroscopic guidance in order to position the lead properly against the endocardial surface of the heart and to prevent inadvertent perforation of the heart wall.
Due to the general linear configuration of standard temporary leads, the distal region of the lead does not easily maintain a position adjacent to the endocardial surface which is needed to maintain sustained electrical capture of the myocardial tissue. Instead the distal region of the lead can easily dislodge and lose capture shortly following placement. The proximal shaft of such a linearly-configured temporary lead is often secured with sutures and adhesive dressing near its manifold to the patient's tissue near the access site to help prevent dislodgement of the lead and loss of capture, however patient movement and inherent motion of the heart tend to easily result in dislodgement of the lead and resultant loss of capture. If the temporary pacing lead should need to be repositioned due to lack of capture as a result of dislodgement, care must be taken and once again requires the use of fluoroscopy, to ensure that the pacing lead does not perforate the myocardial tissue during repositioning. This often requires patient transfer back to the cardiac catheterization laboratory.
Vascular access is obtained via a percutaneous transvenous site through which the temporary pacing lead is performed under fluoroscopic guidance. The lead can be provided percutaneous access using the femoral vein (FV), subclavian vein (SCV), the internal jugular vein (IJV), or other suitable venous access sites. The lead is then advanced through the right atrium (RA) and into the RV. The bipolar lead has a negative electrode or cathode and adjacent positive electrode or anode which are found on the distal segment of the lead positioned to obtain adequate contact with the myocardium of the RV such that the electrical pulse from the pulse generator is transmitted to and captured by the myocardium. Radiation exposure while using fluoroscopy can be detrimental to a patient.
Several complications exist during the placement and operation of temporary pacemaker leads; such complications include myocardial damage, generation of arrhythmias, perforations of the myocardium, tamponade, trauma to the tricuspid valve, and dislocation or dislodgement of the pacing lead with loss of capture. Many of the pacer leads are traumatic and their distal end, wherein the electrodes are located, can penetrate the myocardial tissue or perforate the atrial or ventricular wall of the heart.
What is needed is a temporary pacing lead that is easily placed and is atraumatic to the myocardial tissues of the heart including the tissues of the RA and RV, The lead should be placed without the need for fluoroscopy and its associated inconvenience, time, and radiation, also preferably without the need for echocardiographic guidance. The lead should be configured such that more than one cathode and anode is positioned on the lead such that positioning of the lead does not require precise visualization as required by current standard leads which are placed using fluoroscopy. The lead should not be easily dislodged once it is placed in the RV; the lead should be easily stabilized or held in a stationary position in relation to the access sheath such that dislodgements and loss of capture is reduced. If the lead is displaced, it should be easily repositioned without the need for fluoroscopy or ventricular capture preserved with the use of other electrode pairs in a bipolar configuration or using a monopolar option. The temporary pacing lead should be easily removed following the return of a stable patient rhythm or placement of a permanent pacemaker.